Telescopic crane boom with chain actuation of fly section

ABSTRACT

A telescopic crane boom having a base section, a mid section telescopically received in the base section and a fly section telescopically received in the mid section, a hydraulic cylinder for moving the mid section relative to the base section and chains connected to the base and fly section for extending and retracting the fly section upon actuation of the hydraulic cylinder to extend and retract the mid section. The chains are trained on front and rear sprockets supported by the mid section; the axes of the sprockets are below the bottom of the mid section, the chains are anchored to the bottom of the base section and one chain passes rearwardly through an aperture rearwardly of the anchor. Plural front and plural rear sockets are provided, with a chain for each.

Grove [4 1 May 7,1974

[ TELESCOPIC CRANE BOOM WITH CHAIN ACTUATION OF FLY SECTION [75] Inventor:

[73] Assignee: Fulton Industries, Inc.,

McConnellsburg, Pa.

[22] Filed: Mar. 15, 1972 [21] Appl. No.: 234,937

John L. Grove, Greencastle, Pa.

Primary Examiner-Richard E. Aegerter Assistant Examiner-Joseph E. Valenza Attorney, Agent, or Firm-Irvin A. Lavine [5 7] ABSTRACT A telescopic crane boom having a base section, a mid section telescopically received in the base section and a fly section telescopically received in the mid section, a hydraulic cylinder for moving the mid section relative to the base section and chains connected to the base and fly section for extending and retracting the fly section upon actuation of the hydraulic cylinder to extend and retract the mid section. The chains are trained on front and rear sprockets supported by the mid section; the axes of the sprockets are below the bottom of the mid section, the chains are anchored to the bottom of the base section and one chain passes rearwardly through an aperture rearwardly of the anchor. Plural front and plural rear sockets are provided, with a chain for each.

2 Claims, 6 Drawing Figures PATENTEDHAY 71914 3.809.249

- sum 2 OF 2 [I II I FIG. 5

TELESCOPIC CRANE BOOM WITH CHAIN ACTUATION F FLY SECTION BACKGROUND OF THE INVENTION The present invention relatesto telescopic crane booms for lifting and moving loads, such as a person and/or supplies.

There have long been used various types of cranes, for lifting inert loads and for lifting humans. Where cranes are used primarily for lifting humans, they are often referred to as aerial platforms." Telescopic cranes for both purposes have been used for years, and in the early days of the development of telescopic cranes, the various telescopic sections were caused to move by supplelinks connected to two adjacent sections; such supple links included ropes, wire cables and chains. These constructions were somewhat unweildy, and often required that'the entire extending movement of the telescopic crane sections be in response to a force applied through a single element, such as the shaft of a crank or winch. This required very strong elements and very strong; mountings, which resulted in,

costly and heavy apparatus which was generally too slow and cumbersome, and which was. not easily controlled. In particular, the control of such cranes when of the aerial platform type would be most difficult.

Supplanting the supple link operators of the telescopic sections, in more recent times, were fluid motors in the form of double acting hydraulic cylinders. Hydraulic cylinders replaced the supple links when they had reached the stage of development where they were sufficiently strong and reliable, and hadadequate pumps and valves to respectively power and control them. Typically, where there wasa three section telescopic crane boom, a first hydraulic cylinder was connectedso as tomove the second section-relative to the first section, and a second hydraulic cylinder was connected to move the third section relative to the second section. Thus, in the prior art booms, there were provided one fewer hydraulic cylinders than there were sections, and suitable controls were provided.

The controls of'the hydraulic cylinders which were conventionally provided were in-the formof valves to admit fluidunder pressure tothe cylinders, there being provided a control handle or control'lever for controlling each of the cylinders so that operation of a handle in one direction caused a boomsection to extend, and in the opposite direction causeda-boom section to retract. Independent handles or levers'were provided for the control valves of each of the cylinders. As a -result',

the operator was required to be trainedand-instructed not to extendan outer boom section, of smaller cross section, unless it was necessary andunless the desired reach of the crane couldnotbe obtained-by a-previous extension of an inner boom sectionoflarger cross section. However, despite such training;andinstruction,

from time to time an operator, througheither lack of skill or inadvertence, would extend for example the third or fly section of a three section boom, while the second or mid section was still fully. retracted: as a result, the fly section would beoverloaded, and damage to the boom would result. I

There was formerly proposed asystem for preventing such fly or thirdsection operation; whichinvolved a complex and expensive hydraulic control system, requiring the full extensionof a cylinder controlling the mid section prior to the supplying of fluidto the cylinder which extends the fly section. That solution has not been found to be entirely satisfactory because of the complexity of the hydraulic equipment, and because of the increased expense occurring because of this greater complexity of the hydraulic system.

There have also been provided telescopic booms in which a motor was connected to the base section and mid-section of a three section telescopic boom, with a chain system for extending the fly section, the chain extending from an anchor at the outer end of the base section around a sprocket at the rear of the mid-section having its axis above (or at) the bottom of the midsection, and anchored to the rear of the fly section, and a second part of the chain system extending from the rear of the fly section forwardly around a sprocket at the forward end of the mid-section and thence to an anchor at the outer end of the base section. Such a construction gives rise to interference between the boom section(s) and the chain.

Another consideration pertinent to the construction of telescopic booms for cranes is the weight of the sections and of the parts associated with them, particularly the hydraulic cylinders. In a three section boom, a first hydraulic cylinder will be connected to the first and second sections, to extend and retract the latter, the

cylinder part of the hydraulic cylinder remaining housed in the first section. Similarly, a second hydraulic cylinder will be connected to the second and third sections to extend and retract the latter, and will typi' cally be housed within the second section. Thus, when the second section is extended, the second hydraulic cylinder moves outwardly from the crane pivotal axis, and thus adds its weight to the weight of the second crane boom section at the increased distance from the crane boom pivotal axis. In a typical installation of a 45 foot boom having three sections of substantially 15 feet each, the hydraulic cylinder may have a weight of approximately 500 pounds, and have its center of gravity approximately 22 feet from the pivotal axis, when the boom is in horizontal position. Thus, the hydraulic cylinder for extending the third section will be seen to add considerably to the weight and moment factors of the crane boom.

SUMMARY OF THE INVENTION The present invention provides a telescopic crane boom, which may be of three sections, a first or base section, a second or mid section and a third or fly section, the base section being pivotally connected to a support for raising and lowering movement of the boom about a horizontal axis. The boom sections are each longitudinally extending, and have generally hollow rectangular transverse sections, the base section being of the largest transverse section and receiving telescopically therein the mid section, which in turn receives therein the fly section. A fluid motor in the form of a double acting hydraulic cylinder is provided, being connected to the base section and the mid section in known fashion to extend and retract the latter. The third or fly section is moved by mechanical linkage in response to movement of the second or mid section, the energy for the movement of the fly section being supplied by the hydraulic system including a conventional pump which supplies the noted hydraulic cylinder. This mechanical linkage is in the form of supple links, specifically chains, there being a first chain and a second chain; the second or mid section is provided with arcuate guide surfaces for engagement by the supple link, these specifically being sprockets on which the chains are trained. A front or outer sprocket is positioned adjacent the outer end of the mid section, being supported on the bottom plate of the mid section when it is of the above noted generally hollow transverse rectangular section. A rear or inner sprocket is supported by the mid section near its inner end, and the axes of both of the sprockets are positioned below the level of the bottom plate of the mid section. The first chain extends from an anchor connecting it with the bottom side of the bottom plate of the base section through an aperture at the base section bottom plate and thence rearwardly in the space between the base and mid section bottom plates, around the noted rear sprocket, and having its other end connected to the bottom plate of the fly section near its inner end. The connection is by an anchor, and adjacent to that anchor is another anchor to which the second chain is connected, the second chain extending in the space between the bottom plates of the mid section and fly section, and extendingforwardly, being trained around the front or outer sprocket, and connected by an anchor to the bottom surface of the base section bottom plate, adjacent the first mentioned anchor. When fluid is supplied to the hydraulic cylinder to extend the mid section, the outer sprocket will move outwardly, and pull on the second chain, thereby pulling the fly section and causing it concurrently to extend. Upon reverse operation of the hydraulic cylinder, the mid section will be caused to retract, and the inner sprocket will pull on the first chain, causing it to pull and retract, concurrently, the fly section with the mid section.

Among the objects of the present invention are to provide a telescopic crane boom of comparatively lighter weight and of the same strength as previous booms. Another object of this invention is the provision of a crane boom havingextension and retraction equipment of lighter weight than heretofore. Still another object of the present invention is to provide a telescopic boom for a crane in which supple links are provided for extending and retracting one section in response to extension and retraction of another section, with provision of guides for the supple links positioned to avoid interference of the movement thereof.

' Other objects and many of the attendant advantages of the present invention will be readily understood from the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a mobile crane with telescopic boom in accordance with the present invention.

FIG. 2 is an enlarged longitudinal view with parts in section of the boom shown in FIG. 1.

FIG. 3 is an enlarged cross sectional view taken on the line 33 of FIG. 2.

FIG. 4 is an enlarged cross sectional view taken on the line 4-4 of FIG. 2.

FIG. 5 is an enlarged cross sectional view taken on the line 5--5 of FIG. 2.

FIG. 6 is an enlarged cross sectional view taken on the line 6-6 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, wherein like or corresponding numerals are used to designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a crane generally designated 10, crane 10 being illustrated as a mobile or vehicle-mounted crane, including a vehicle 11, a turn table 12 and outriggers 13. The telescopic and extensible crane boom is generally designated 15, and comprises a first or base section 16, a second or mid section 17 and a third or fly section 18. The outer end of the fly section 18 is provided with a supporting nose 19, to which is attached a basket aerial platform 20. Controls are preferably provided in the aerial platform 20 for controlling the extension and retraction of the sections 17 and 18, and other controls may be provided as is well known to those skilled in the art, as for raising and lowering the boom 15 and for rotating the entire boom including the turn table 12. By way of illustration, raising and lowering cylinders 21 and 22 may be seen connected to the turn table 12 and to the base section 16 of boom 15.

Referring now to FIG. 2, the telescopic boom 15 is shown in cross section, and in its retracted position. Thus, each of the hollow boom sections of lesser strength and of similar transverse hollowcross sectional dimensions is telescopically received in the next boom section of larger cross section and of higher strength. The base section 16 is provided with depending ears, such as 26, for connection to a first cylinder for-causing raising and lowering of the boom 15, a second ear 27 being provided for receiving a pivot pin (not shown) on which the boom 15 may be raised and lowered, and a third ear and axle construction 28 for connection with a lift cylinder, such as thelift cylinder 21 shown in FIG. 1. On its top, the base section 16 is shown provided with a reinforcing plate 29, and lying thereon is a conduit group 30 which can provide for suitable electricala'nd/or hydraulic conduits extending from the aerial platform 20 to the various elements to be controlled. As may be seen in FIG. 3, base section 16 is provided with side reinforcing plates 31 and 32. The transverse cross sectional shape of base section 16 may also be seen in FIG. 3, and comprising a generally hollow rectangular cross sectionwhich includes a top plate 16a, side plates 16b and 16c and a bottom plate 16d. 1

Referring again to FIG. 2, within base section .16 there may be seen the mid section 17, which is provided at its inner end witha wear pad 33positioned between the sections 16 and 17; in FIG. 3, it may be seen that two such wear-pads 33 are provided. The fly section 18 is positioned inwardly of the mid section 17, and a wear-pad 34 is provided between them. Inwardly of the fly section 18 there is a hollow housing 35. B01- low housing 35 is provided with a flange 36 at its inner end, to the left as shown in FIG. 2, which flange 36 is secured to a housing mounting plate 37 that is in turn secured to the mid section 17 adjacent its inner or rear end. The hollow housing mounting plate 37 may be seen in FIG. 3 to be generally in the shape of an open rectangle, there also being seen in' FIG. 3 a plurality of bolts which serve to secure together the flange 36 and mounting plate 37. A fluid motor 40, specifically in the form of a double acting hydraulic cylinder, is also shown in FIGS. 2 and 3, passing through the mounting plate 37. Also shown in FIG. 3 are additional wear plates 38 and 39 provided between the base section 16 and the mid section 17.

At its rear end, fluid motor 40 is provided with a transverse tube 41 within which is a pivot pin 42; pivot pin 42 is connected'to the base section at the inner or rear end thereof.

The fluid motor 40 at its outer end has an extending rod 43 on which is a tube 44, a pin 45 being received in the tube 44 and being supported, as shown in FIG. 6, by a pair of spaced apart support plates 46 and 47. The support plates 46 and 47 are fixed to the hollow housing 35 at its outer end. Hence, actuation of fluid motor 40 will cause the mid section 17 to be linearly moved relative to base section 16, through the connection provided by the hollow housing 35, flange 36 and mounting plate 37.

A mechanical linkage system is providedfor extending the fly section 18 concurrently with extension of the mid section 17, and for retracting fly section 18 concurrently with mid section 17, the noted linear movement of fly section 18 being effected by the mid section 17 actuating mechanical linkage. Thus, as shown in FIGS. 2 and 4, the mid section 17 has at its bottom plate 17d an aperture 51 which is adjacent to its inner end, just outwardly or forwardly of-the mounting plate 37. The aperture 51 has mounted beneath it a sprocket mounting assembly 52, generally secured to the bottom of the bottom plate 17d. Mounting assembly 52 has journalled therein a sprocket shaft 53 which carries a pair of rear or inner sprockets 54 in transversely spaced relationship. At its outer end, the mid section 17 is provided with a mounting assembly 56 suitably secured to the bottom plate 17d (see FIG. 5), there being a sprocket shaft 57 therein, and having a pair of spaced outer or forward sprockets 58'journalled therein. The sprockets 54 and 56 serve as guides,-and it will be seen that they revolve about shafts 53 and 57 which have their axes below the level of the bottom plate 17d of mid section 17. This placement of the sprocket shafts 53 and 57 is important to avoid interference between the chains and the fixed boom elements, to thereby insure long operation of the boom, without excessive deterioration or wear.

The base section 16 near its outer end is provided with a first anchor 61 on the bottom surface of the bottom plate 16d thereof. inwardly or to the rear of anchor 61, bottom plate 16d has an aperture 62, and a pair of chains 60 extend from the anchor 61 through the aperture 62 and thence rearwardly, in the space between the bottom 16d of base section 16 and the bottom plate 17d of mid section 17, to the sprockets 54, shown in FIGS. 2 and 4. The chains 60 are trained on the sprockets 54 and pass therearound, and thence forwardly to an anchor 63 fastened to the bottom of the bottom plate 18d of fly section 18. Just forwardly of the anchor 63 is an anchor 64, similarly connected to the bottom of the bottom plate 18d, and connected to the anchor 64 are a pair of chains 65 which extend forwardly from the anchor 64 in the space between bottom plates 18d and 17d, and to the sprockets 58, the chains 65 extending around sprockets 58 and being connected by an anchor 66 to the bottom surface of the bottom plate 16d of base section 16. As may be seen, the anchors 61 and 66 are in adjacent relationship, anchor 66 being closer to the outer end of base section 16 than anchor 61, and both are in a position such that the ends of the chains are accessible, to permit adjustment.

Referring again to FIG. 5, the above referenced wear-pads 34 may be seen, as well as additional wearpads 38. All wear-pads are of generally known construction, and preferably of a suitable material to permit relative sliding movement between the various boom sections, while being long lasting in use.

In operation, a pump will supply fluid under pressure to the fluid motor 40 through a suitable control valve, to thereby actuate it. In the present instance, since fluid motor 40 is in the form of a double acting hydraulic cylinder, the piston therein will be caused to move, thereby increasing the space between the pins 42 and 45 to which the fluid motor 40 is connected, thereby linearly extending the mid section 17, due to the aforementioned connection from pin 45 to the hollow housing and thence to the mid section 17, pin 42 being anchored to base section 16. As mid section 17 is extended, the sprockets 58 will move with it, away from the base section 16. This movement of the sprockets 58 will exert a pull on the chain 65, which will function as a supple link. Since one end of the chain 65 is immovably fixed by the anchor 66, the upper run of chain 65 as shown in FIG. 2 will exert a force on anchor 64, and through it the fly section 18, causing fly section 18 to be linearly extended concurrently with the linearly extending movement of mid section 17. Such extension in a concurrent manner by the mid section 17 in fly section 18 may continue to the limit of the physical dimensions of the apparatus, which thereby. determines the full extension of the boom 15. Upon operation of the fluid motor in the opposite direction, through suitable control valve means, forces applied to the pins 42 and will cause linear retraction of mid section 17, thereby causing inward movement of the sprockets 54 toward the inner end of base section 16, and the supple link formed by the chains will be acted upon, thereby exerting a pull on the anchor 63 and causing the fly section 18 to be concurrently retracted with the retracting motion of mid section 17.

It will be understood that during extension of the boom sections 17 and 18, the sprockets 54 will be caused to move outwardly, and a portion of the chain 60 will thereby pass around the sprocket, from the space between lower plates 17d and 16d to the space between lower plates 18d and 17d. Conversely, upon retracting movement of the boom sections 17 and 18,

a portion of the chains will be caused to move from the bottom of bottom plates 16d into the space between bottom plates 18d and 17d.

The telescopic crane boom herein disclosed is provided with but a single fluid motor, which causes concurrent extension and retraction of both the mid section 17 and fly section 18, due to its connection to base section 16 and mid section 17, and due to mechanical linkage which is connected to the fly section 18, and which mechanical linkage moves in response to and is actuated by movement of the mid section 17. Thus, there has been provided a telescopic crane boom which cannot be over stressed due to extension of the lighter weight and smaller cross section fly section while the stronger and larger cross section boom mid section is in the retracted position.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

What is claimed is:

l. A boom for a crane comprising:

a first section telescopically receiving a second section, said second section telescopically receiving a third section, said sections being longitudinally extending and having hollow transverse cross sections,

fluid motor means connected to said first and second sections for extending and retracting said second section,

front and rear sprocket means carried by said second section adjacent the outer and inner ends thereof respectively with their axes transverse to said boom sections and lower than the bottom of said second section,

first chain means, means for anchoring one end of said first chain means to said first section adjacent the outer end thereof, said first chain means extending around said rear sprocket means, means anchoring the other end of said first chain means to said third section adjacent the inner end thereof,

second chain means, means for anchoring one end of said second chain means to said first section adjacent the outer end thereof, said second chain means extending around said front sprocket means, means anchoring the other end of said second chain means to said third section adjacent the inner end thereof, and an aperture in said first section adjacent the outer end thereof rearwardly of said anchors of said first and second chain means, said anchors on said first section being on the lower surface of the bottom of said first boom section and said first chain means extending through said aperture, whereby the ends of said chain means are accessible. 2. The boom of claim 1, wherein each said chain means and sprocket means comprises plural chains and plural sprockets. 

1. A boom for a crane comprising: a first section telescopically receiving a second section, said second section telescopically receiving a third section, said sections being longitudinally extending and having hollow transverse cross sections, fluid motor means connected to said first and second sections for extending and retracting said second section, front and rear sprocket means carried by said second section adjacent the outer and inner ends thereof respectively with their axes transverse to said boom sections and lower than the bottom of said second section, first chain means, means for anchoring one end of said first chain means to said first section adjacent the outer end thereof, said first chain means extending around said rear sprocket means, means anchoring the other end of said first chain means to said third section adjacent the inner end thereof, second chain means, means for anchoring one end of said second chain means to said first section adjacent the outer end thereof, said second chain means extending around said front sprocket means, means anchoring the other end of said second chain means to said third section adjacent the inner end thereof, and an aperture in said first section adjacent the outer end thereof rearwardly of said anchors of said first and second chain means, said anchors on said first section being on the lower surface of the bottom of said first boom section and said first chain means extending through said aperture, whereby the ends of said chain means are accessible.
 2. The boom of claim 1, wherein each said chain means and sprocket means comprises plural chains and plural sprockets. 